How to Install a window Air Conditioner in a wall

[fred.flintstone]

I have a shed/workshop that is too hot to use. I have a window AC, but it's too big for the windows in the shed. I've decided to install it in the wall. The walls are just studs with a plywood siding. It's just rough studs inside, so it's just a matter of cutting thru the plywood siding. The problem is how to seal it so rain and insects dont get in around it. Even if I cut it fairly tight, there will still be a gap, and water will come in during rains, and damage the wood. I suppose several tubes of silicone caulk would work, but that would make it impossible to remove for repairs.

What's the trick to this?

[rlz]

I had the same scenario a few years ago after I built my workshop. I ended up cutting a hole in the siding just big enough for the A/C to fit though it. I then trimmed it out with some 1x4's that matched the corner boards of the workshop. I just caulked where the trim touched the A/C and where the trim touched the siding. If it ever needs to be removed, I'll just cut the caulking with a razor blade and remove the trim. The inside has OSB covering the walls, so I just cut some quarter inch thick slices of a 2x4 and used them towrap around the A/C to seal it inside the shop.

Having the A/C definitely makes a difference in there during the summer.

Rob

[hrhofmann]

What Rob said, plus, make sure to mount the AC sloping downward on the outside so that rain and internal condensation go out not into your workshop If you can't cut an opening within 1/8 inch of the dimensions of the AC, you shouldn't be building a workshop. One or two tubes of caulking should be more than enough to fill the 1/8 inch gap. Use backing materials such as a foam rubber strip to keep the caulking frorm going into the hole without stopping.

[DerbyDad03]

One thing to make sure of is that the side vents are not blocked by the wall or any trim that you install.

Wall mount units, especially ones that fit into a sleeve, have all of the venting on the rear. Check your unit to be sure it can be mounted in the wall without blocking the side vent.

I know it's an extra expense, but have you considered purchasing a new- construction window from a home center and installing that first?

Better yet, if you have a house parts/renovation outlet anywhere nearby, I'll bet you could get a used shop-grade window pretty darn cheap.

You'd have the added advantage of more light, ease of removing the AC in the winter (if you have winter) and of course, no fussing around with trying to make the unit work where it wasn't meant to.

[Dave M.]

Robin,

Pick a shady spot where the AC can do it's business. Cut a hole of the appropriate size ( maybe 1/8" larger than the AC unit). Nail up 2X4s to frame the hole and attach to the studs. Don't caulk, use sticky backed foam tape on the inside. This tape will need to be replaced every 4-5 yrs. On the outside paint the siding to protect it from water and surround the opening with molding to make it look snazzy.

Dave M.

[dpb]

Basically what they said, but I'd flash it as well--probably use a piece of the adhesive flashing--before the finishing trim since it's intended as a permanent installation. Essentially treat it as if were installing a new window.

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[DerbyDad03]

re: "If you can't cut an opening within 1/8 inch of the dimensions of the AC, you shouldn't be building a workshop"

He said he *has* a shed/workshop, not that he's building one.

Obviously, there's more to this than just cutting a hole and caulking the gap.

Without a window, there's no sill to rest the unit on. The unit can't be (OK, shouldn't be) just balanced on the plywood.

A sill will be needed to rest the unit on and a header installed to keep the unit from tipping backward. Obviously not a huge endeavor, but certainly more than just cutting a hole in the wall.

[Doug]

Based on memory of my dad (carpenter) did many moons ago, I'd say what you got for advice is valid. The only thing is make sure, if it's important to you, to not allow the unit to be pushed back into the workshop to prevent burglary. Not sure how to do this but I'm sure someone else knows or Google around.

[clare]

put a bicycle inner tube around the air conditioner and a frame on the outside about 1/2 inch bigger all around than the air conditioner. Stich the tube into the gap between the unit and the frame and inflate enough to give a tight seal.

[gregz]

When I mounted one in my trailer vibration was a consideration. Mine floats. PVC siding cut to form a curved water shed on top. Sides were filled in with stick on black foam insulation tape. Just part of side vents blocked, but covered inside section. Bottom on pads, and pushed down on inside top. Too much slant will decrease efficiency if the splash wheel does not get wet.

Greg

[Sonny]

As someone has said, use backer rod to seal the gap around the air conditioner and "window" framing.

Make your finished opening about 1/2" larger, on all sides, than your air conditioner's housing. You'll need the extra space for possible reinstallation modifications, later, if need be.

Depending on your unit, some older units will sweat (condensate) on their sides and bottom, causing moisture to drip onto the window sill and down the siding of the shop's exterior.... and maybe on the interior, also. If this happens, reinstall with 1/4" spacers (rods) between the air conditioner housing and sill. Insert sheet metal (flashing) on the sill to prevent the condensation from wetting the sill and other areas, there. Backer rod the lower interior gap (where the spacers are), leaving the exterior's lower gap open for condensation drainage.

The housing is supposed to help prevent condensation from forming, this way, but with some older units, the insulation on the housing (if originally there) will have become old, worn away and/or disfunctional, hence the unit may condensate onto the wall's/window's structure.

[dpb]

...

Use flash first rather than waiting to find out if should have later... :)

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[Evan]

First off, your building is too hot to use because it is just plywood and studs... Spend money on adding some insulation, vapor barrier and an interior wall surface... Otherwise your AC unit will definitely need some repairs fairly soon trying to keep up with the cooling load you are saddling it with...

Secondly, you need a sleeve rated unit when you are installing an AC unit through the wall... The sleeve is installed to the properly built wall structure and weatherproofed and the compatible AC unit slides right in...

If you are so dead set on re-purposing the specific AC unit you have available rather than buying one properly suited to the application, then buy and properly install a window large enough to allow the AC you have to be used in the manner it was designed to be used...

[clare]

A sleave type is only required for thicker walls. They are a lot harder to find, and more expensive.

Just frame in a hole the size an open window would need to be to install the window air conditioner, complete with sloped sill, and install the air conditioner as if it was in a window. You MIGHT want to put an extended flashing as a "drip guard" across the top to redirect falling rain.

Insulating the shop - particualarly the roof - would definitely be a good idea that will pay for itself quickly. DO NOT use beaded styrene board insulation (styrofoam) and leave it uncovered.